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<H1 ALIGN="CENTER">Module mod_auth_digest</H1>

This module is contained in the <CODE>mod_auth_digest.c</CODE> file, and is
not compiled in by default. It is only available in Apache 1.3.8 and
later. It provides for user authentication using MD5 Digest
Authentication.

<P>Note this is an updated version of <A
HREF="mod_digest.html">mod_digest</A>. However, it has not been
extensively tested and is therefore marked experimental. If you use this
module, you must make sure to <em>not</em> use mod_digest (because they
share some of the same configuration directives).


<MENU>
<LI><A HREF="#authdigestfile">AuthDigestFile</A>
<LI><A HREF="#authdigestgroupfile">AuthDigestGroupFile</A>
<LI><A HREF="#authdigestqop">AuthDigestQop</A>
<LI><A HREF="#authdigestnoncelifetime">AuthDigestNonceLifetime</A>
<LI><A HREF="#authdigestnonceformat">AuthDigestNonceFormat</A>
<LI><A HREF="#authdigestnccheck">AuthDigestNcCheck</A>
<LI><A HREF="#authdigestalgorithm">AuthDigestAlgorithm</A>
<LI><A HREF="#authdigestdomain">AuthDigestDomain</A>
<LI><A HREF="#usingdigest">Using Digest Authentication</A>
</MENU>
<HR>


<H2><A NAME="authdigestfile">AuthDigestFile</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestFile <EM>filename</EM><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>

<P>The AuthDigestFile directive sets the name of a textual file containing
the list of users and encoded passwords for digest authentication.
<EM>Filename</EM> is the absolute path to the user file.

<P>The digest file uses a special format. Files in this format can be
created using the "htdigest" utility found in the support/ subdirectory of
the Apache distribution.

<HR>

<H2><A NAME="authdigestgroupfile">AuthDigestGroupFile</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestGroupFile <EM>filename</EM><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P>The AuthDigestGroupFile directive sets the name of a textual file
containing the list of groups and their members (user names).
<EM>Filename</EM> is the absolute path to the group file.

<P>Each line of the group file contains a groupname followed by a colon,
followed by the member usernames separated by spaces. Example:
<BLOCKQUOTE><CODE>mygroup: bob joe anne</CODE></BLOCKQUOTE>
Note that searching large text files is <EM>very</EM> inefficient.

<P>Security: make sure that the AuthGroupFile is stored outside the
document tree of the web-server; do <EM>not</EM> put it in the directory
that it protects. Otherwise, clients will be able to download the
AuthGroupFile.

<HR>

<H2><A NAME="authdigestqop">AuthDigestQop</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestQop <EM>none | 1*{ auth | auth-int }</EM><BR>
<A
 HREF="directive-dict.html#Default"
 REL="Help"
><STRONG>Default:</STRONG></A> <CODE>AuthDigestQop auth</CODE><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P>The AuthDigestQop directive determines the quality-of-protection to use.
<EM>auth</EM> will only do authentication (username/password);
<EM>auth-int</EM> is authentication plus integrity checking (an MD5 hash
of the entity is also computed and checked); <EM>none</EM> will cause the
module to use the old RFC-2069 digest algorithm (which does not include
integrity checking). Both <EM>auth</em> and <EM>auth-int</EM> may be
specified, in which the case the browser will choose which of these to
use. <EM>none</EM> should only be used if the browser for some reason
does not like the challenge it receives otherwise.

<P><STRONG><EM>auth-int</EM> is not implemented yet</STRONG>.

<HR>

<H2><A NAME="authdigestnoncelifetime">AuthDigestNonceLifetime</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestNonceLifetime <EM>&lt;time&gt;</EM><BR>
<A
 HREF="directive-dict.html#Default"
 REL="Help"
><STRONG>Default:</STRONG></A> <CODE>AuthDigestNonceLifetime 300</CODE><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P>The AuthDigestNonceLifetime directive controls how long the server
nonce is valid. When the client contacts the server using an expired
nonce the server will send back a 401 with <code>stale=true</code>. If
<EM>&lt;time&gt;</EM> is greater than 0 then it specifies the number of
seconds the nonce is valid; this should probably never be set to less
than 10 seconds. If <EM>&lt;time&gt;</EM> is less than 0 then the nonce
never expires.

<!-- Not implemented yet
If <EM>&lt;time&gt;</EM> is 0 then the nonce may be used exactly once
by the client. Note that while one-time-nonces provide higher security
against replay attacks, they also have significant performance
implications, as the browser cannot pipeline or multiple connections
for the requests. Because browsers cannot easily detect that
one-time-nonces are being used, this may lead to browsers trying to
pipeline requests and receiving 401 responses for all but the first
request, requiring the browser to resend the requests. Note also that
the protection against reply attacks only makes sense for dynamically
generated content and things like POST requests; for static content
the attacker may already have the complete response, so one-time-nonces
do not make sense here.
-->

<HR>
<H2><A NAME="authdigestnonceformat">AuthDigestNonceFormat</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestNonceFormat <EM>???</EM><BR>
<A
 HREF="directive-dict.html#Default"
 REL="Help"
><STRONG>Default:</STRONG></A> <CODE>AuthDigestNonceFormat ???</CODE><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P><STRONG>Not implemented yet.</STRONG>
<!--
<P>The AuthDigestNonceFormat directive determines how the nonce is
generated.
-->

<HR>
<H2><A NAME="authdigestnccheck">AuthDigestNcCheck</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestNcCheck <EM>On/Off</EM><BR>
<A
 HREF="directive-dict.html#Default"
 REL="Help"
><STRONG>Default:</STRONG></A> <CODE>AuthDigestNcCheck Off</CODE><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> server config<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> <EM>Not applicable</EM><BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P><STRONG>Not implemented yet.</STRONG>
<!--
<P>The AuthDigestNcCheck directive enables or disables the checking of the
nonce-count sent by the server.

<P>While recommended from a security standpoint, turning this directive
On has one important performance implication. To check the nonce-count
*all* requests (which have an Authorization header, irrespective of
whether they require digest authentication) must be serialized through
a critical section. If the server is handling a large number of
requests which contain the Authorization header then this may noticeably
impact performance.
-->

<HR>
<H2><A NAME="authdigestalgorithm">AuthDigestAlgorithm</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestAlgorithm <EM>MD5 | MD5-sess</EM><BR>
<A
 HREF="directive-dict.html#Default"
 REL="Help"
><STRONG>Default:</STRONG></A> <CODE>AuthDigestAlgorithm MD5</CODE><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P>The AuthDigestAlgorithm directive selects the algorithm used to calculate
the challenge and response hashes.

<P><STRONG><EM>MD5-sess</EM> is not correctly implemented yet</STRONG>.
<!--
<P>To use <EM>MD5-sess</EM> you must first code up the
<VAR>get_userpw_hash()</VAR> function in <VAR>mod_auth_digest.c</VAR> .
-->

<HR>
<H2><A NAME="authdigestdomain">AuthDigestDomain</A></H2>
<A
 HREF="directive-dict.html#Syntax"
 REL="Help"
><STRONG>Syntax:</STRONG></A> AuthDigestDomain <EM>URI URI ...</EM><BR>
<A
 HREF="directive-dict.html#Context"
 REL="Help"
><STRONG>Context:</STRONG></A> directory, .htaccess<BR>
<A
 HREF="directive-dict.html#Override"
 REL="Help"
><STRONG>Override:</STRONG></A> AuthConfig<BR>
<A
 HREF="directive-dict.html#Status"
 REL="Help"
><STRONG>Status:</STRONG></A> Base<BR>
<A
 HREF="directive-dict.html#Module"
 REL="Help"
><STRONG>Module:</STRONG></A> mod_auth_digest<BR>
<A
 HREF="directive-dict.html#Compatibility"
 REL="Help"
><STRONG>Compatibility:</STRONG></A> Available in Apache 1.3.8 and later

<P>The AuthDigestDomain directive allows you to specify one or more URIs
which are in the same protection space (i.e. use the same realm and
username/password info). The specified URIs are prefixes, i.e. the client
will assume that all URIs "below" these are also protected by the same
username/password. The URIs may be either absolute URIs (i.e. inluding a
scheme, host, port, etc) or relative URIs.

<P>This directive <em>should</em> always be specified and contain at least
the (set of) root URI(s) for this space. Omiting to do so will cause the
client to send the Authorization header for <em>every request</em> sent to
this server. Apart from increasing the size of the request, it may also
have a detrimental effect on performance if "AuthDigestNcCheck" is on.

<P>The URIs specified can also point to different servers, in which case
clients (which understand this) will then share username/password info
across multiple servers without prompting the user each time.


<HR>

<H3><A NAME="usingdigest">Using Digest Authentication</A></H3>

<P>Using MD5 Digest authentication is very simple. Simply set up
authentication normally, using "AuthType Digest" and "AuthDigestFile"
instead of the normal "AuthType Basic" and "AuthUserFile"; also,
replace any "AuthGroupFile" with "AuthDigestGroupFile". Then add a
"AuthDigestDomain" directive containing at least the root URI(s) for
this protection space. Example:

<PRE>
  &lt;Location /private/&gt;
  AuthType Digest
  AuthName "private area"
  AuthDigestDomain /private/ http://mirror.my.dom/private2/
  AuthDigestFile /web/auth/.digest_pw
  require valid-user
  &lt;/Location&gt;
</PRE>

<P><strong>Note:</strong> MD5 authentication provides a more secure
password system than Basic authentication, but only works with supporting
browsers. As of this writing (July 1999), the only major browsers which
support digest authentication are <A
HREF="http://www.microsoft.com/windows/ie/">Internet Exploder 5.0</A> and
<A HREF="http://www.w3.org/Amaya/">Amaya</A>. Therefore, we do not
recommend using this feature on a large Internet site. However, for
personal and intra-net use, where browser users can be controlled, it is
ideal.

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